The early evolution of the mammalian forebrain can be best examined by comparing the progressive changes occurring in brain morphology among ancestral mammal-like reptiles (therapsids). Endocranial brain casts are currently uncommon due to the lack of adequately prepared fossil skull, their unavailability, and the generally held belief that the walls of the endocranium are poorly ossified. The purpose of this project is to prepare skulls acquired at the Smithsonian Institution for new brain casts. Initial preparations indicate that ventrally the endocranium is partially cartilaginous between the basisphenoid and sphenethmoid bones; however, the preserved endocranium is complete enough to provide valuable information about the size, shape, structure, and encephalization of the brain of mammal-like reptiles. In addition, it is clear that both carnivorous (cynodont) and herbivorous (dicynodont) therapsids will have to be compared for an evaluation of the impact of life stype (solitary vs. gregarious groups) upon brain morphology. Current preparations suggest that the brain of dicynodonts is well within the range of reptilian encephalization. The pineal was prominent and contiguous with a well-developed third eye which rested in a cone-shaped parietal foramen posterior to the parietal-frontal suture.